by Andrew Parker

This book discusses the Cambrian explosion, putting forth the theory that it was due to the evolution of the eye.

I found that the evidence he presented was not compelling for his thesis. He shows that evolution of the eye and the Cambrian explosion may have occurred at the same time, but that correlation does not translate into causation for me.

However, he does review a great deal of evidence. The post-Cambrian was the great age of the trilobite. I learned a good deal about these creatures, and the likely eco-system in which they lived.

Nevertheless, I can think of other theories for why the Cambrian explosion occurred. Perhaps there was a constellation of genes that allowed for hard shells and bones that fossilized. Perhaps the atmosphere and the chemistry of the ocean had changed to allow the creation of hard parts. Perhaps the linage that lead to most large animals had recently duplicated its HOX genes, and those new genes powered the explosion with new design elements. Perhaps the linage evolved a new, successful method of intercellular communication that allowed for more flexible, and larger, designs. Maybe the immune system evolved to fight off infections from parasites, bacteria and viruses.

Parker presents plenty of evidence for why the trigger for the Cambrian could be vision, and he presents it well. He does not present much evidence, however, that would make some of the other possible theories highly unlikely.

Addendum from 2012:

Having read "The Plausibility of Life", I am even less convinced by Parker's arguments. It is more likely that the development of HOX gene controlled compartments in the embryo lead to the Cambrian explosion.